Personnel working at height are normally required to wear a body harness. The body harness is entwined around parts of the wearer's body in order to ensure that the wearer's body is held securely within the body harness. The body harness is typically attached to one end of a lanyard and the other end of the lanyard is then attached to a secure anchorage. An alternative arrangement is where the body harness is attached to a line that can be extracted from or retracted into a drum that can rotate within a housing that is then attached to a secure anchorage. Extraction of the line from the drum is normally achieved by pulling the line whereas retraction of the line into the drum occurs automatically due to the action of a torsion spring tending to rotate the drum to retract the line. If the line is extracted from the drum quickly, as would be the condition in a fall event, pawls within the housing engage on the drum and stop the drum from any further rotation until the load on the line due to the pulling action is removed. The secure anchorage could be any appropriate anchorage on a structure or building or it could be part of a further fall arrest system such as a cable system whereby the secure anchorage may be able to move along the length of the cable whilst the anchorage is securely attached to said cable thereby allowing access to areas within the proximity of the length of the cable. In any fall arrest arrangement, it is usual for an energy absorber to be attached between the body harness and secure anchorage and for deployment of such an energy absorber to be achieved within a given load limit in order to limit loading on the body of the faller. Many lanyards have a flat rectangular cross section and the energy absorber is incorporated by folding and then stitching together a part of the length of the lanyard such that when the lanyard is subjected to a sufficient tensile loading between either end, the stitching progressively breaks causing the effective length of the lanyard to extend whilst such tensile loading is sustained thereby absorbing energy. The energy absorber associated with the line extracted from or retracted onto a drum is often incorporated between the drum and its housing by allowing the drum to rotate to extract line from the drum after the pawls have engaged on condition that the tensile loading on the line exceeds a threshold limit that is less than the given limit for loading on the body of the faller. The threshold load is often mechanically determined by friction applied between the drum and it's housing whereby the drum can rotate if, and as long as, the load on the line is sufficient to overcome the resisting load due to the friction.
Fall arrest systems and equipment generally allow a person to access the edge of a building or structure where there is a possibility of a fall occurring. In the unfortunate event that someone should accidentally fall, the fall arrest equipment arrests the fall of the faller leaving the faller suspended at height close to the edge of the building or structure. The faller is secured within a harness that is then attached to lanyard or retractable line that is then attached to a secure anchorage. During the fall arrest process, the energy absorber located between the faller and the secure anchorage will normally deploy depending on the fall energy that needs to be absorbed thereby limiting the load on the faller's body. Whilst the faller is safely arrested and the load applied on the faller's body is limited, the physical demands placed on the human body during a fall event are nevertheless significant particularly if the faller is light in weight or is in a relatively poor state of health. However, there are further serious complications experienced by a faller suspended at height in a harness following the fall event. Motionless suspension in a harness for even a very short time, sets up a blood venous pooling effect, which becomes dangerous leading to unconsciousness and eventually death in as little as ten minutes. Various research studies have been carried out confirming the dangers of motionless suspension and there is now general agreement that it is vital to rescue and recover a faller as quickly as possible to avoid the onset of serious life threatening complications.
There are various methods currently used for rescuing fallers but none of these is generally satisfactory. The most common method is to call out the fire services. The speed of response depends on a number of factors such as where the fall has occurred and its distance from the nearest fire services depot, the availability of fire service resources at the time of the fall incident and whether the nearest fire services depot has the specialist equipment such as mobile platforms and lifting equipment for rescuing a person suspended at height. The specialist equipment tends to be relatively expensive and used less often than the standard firefighting equipment and is usually only available at a selection of fire service depots. All these factors make it difficult to predict how long the fire services will take between being alerted to a fall event and being in a position to begin to lower the suspended person to the ground. Generally, the response times vary widely between about 10 minutes at best and up to as much as an hour. A further problem can be to gain access to the specific location on the perimeter of a building where a fall has occurred. Many buildings are sited close to neighboring buildings or there are obstructions such as barriers all of which impede speedy access of the appropriate height rescue equipment to a fall location.
Another rescue method is for a rescuer equipped with descending apparatus to be lowered, or to lower himself, alongside the faller and to attach the faller's harness to the descending apparatus. The rescuer then cuts the faller's lanyard usually with a knife, so that the faller's weight is transferred to the descending apparatus. Having cut the faller's lanyard, the rescuer descends with the faller. This method has several disadvantages not least of which is the need for the rescuer to expose himself to significant risks. The rescuer will also need to have received substantial technical and physical training in order to carry out this rescue method. The training is generally expensive and so tends to be limited to a select few thereby increasing the possibility that a person properly qualified to carry out such a rescue procedure may not be immediately available at the time of a fall event.
A further rescue method is to attach the faller's harness to a lifting apparatus such as provided in GB2376009 and to lift the faller back to the top of the building or to the original location of the cable fall arrest system. This method presents a number of problems. Firstly, the harness attachment point of a person suspended at height after being arrested from a fall is likely to be two or more meters below the edge of the building. Any attempt to attach lifting cable to the attachment point from a position at the top of the building will typically compromise the safety of the rescuer. GB2376009 shows a substantial and convenient anchorage point in the form of an overhanging beam. In most typical locations where personnel work whilst attached to fall arrest systems or equipment there is unlikely to be a convenient and appropriate anchorage sufficiently elevated above both the faller and the edge of a building to enable the suspended faller to be lifted clear of the edge before being recovered to the level from which the fall occurred. The time needed to erect such a beam following a fall event would be significant. However, even if the faller were to be successfully raised and recovered, there is still the problem of transporting him or her easily and safely to the ground in order to enable him or her to access appropriate emergency services in the likely event that he or she has sustained injuries.
In either of the aforementioned rescue methods, not including the method using the fire services, there is a need to locate and transport the rescue system apparatus to the site where the fall has occurred and to unpack and prepare the apparatus before the rescue process can begin. Since the need to undertake a rescue is thankfully rare, there is considerable potential for problems that could cause further delays such as locating the rescue apparatus, ensuring that the package containing the apparatus is complete and that the rescue equipment is properly maintained. Also, as already mentioned, the rescue methods generally require a high level of personnel training and so there is the need to ensure that there is always an appropriately qualified rescuer at hand when height access work is being carried out.
Taking all the above factors into account there is considerable advantage in arranging the rescue apparatus to be an integral part of the faller's personal equipment so that the apparatus is immediately available at the site of the fall and ready to be operated on by the faller and/or a rescuer.